Project Summary Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease causing progressive muscle weakness and impairments in swallowing (dysphagia). Dysphagia leads to malnutrition, dehydration, tracheal aspiration and pneumonia that contribute to 26% of ALS mortality. The current proposal is strongly motivated by fundamental knowledge gaps that have contributed to sub-optimal clinical care of individuals with ALS and a lack of formal practice guidelines in the management of progressive swallowing impairment in ALS. The overarching goal of this work is to improve clinical practice by 1) increasing our understanding of governing mechanisms and progression of dysphagia in ALS and 2) identification of sensitive biomarkers of swallowing dysfunction to build a clinical dysphagia risk index tool. We will perform serial instrumental swallowing evaluations in 100 individuals with ALS (50 bulbar-onset, 50 spinal-onset) from disease diagnosis to feeding-tube dependence and provide critical longitudinal data to help establish the first time-course model of ALS swallowing decline. Such a model is needed to guide best practice recommendations, optimal timing of interventions, for planning and design of future clinical trials, and for interpretation of experimental treatment effects. We will also test the discriminant ability and clinical utility of a set of promising clinical markers of swallowing decline that are pragmatically designed for easy dissemination into ALS clinical settings. Our long- term goal is to improve clinical care of swallowing disorders in ALS. The proposed study will deliver new insights into the pathophysiologic mechanisms of unsafe and inefficient swallowing in ALS to drive the development of future intervention strategies and lead to earlier and more accurate identification of swallowing impairment. Earlier identification and better treatment strategies for swallowing dysfunction in ALS will lead to improvements in oral intake, nutrition, pulmonary health and quality of life and ultimately reduce aspiration pneumonia associated mortality in this challenging population.